1. Field of the Invention
This invention relates to a capability control apparatus for a cooling system provided with a direct expansion type evaporator, such as an absorption refrigerating machine.
2. Description of the Prior Art
In an absorption refrigerating machine provided with a direct expansion type evaporator, water or other heating medium is generally used as means for taking out refrigerating or cooling capabilities that have been developed in the evaporator. Further, the control of the amount of solution to be circulated and the amount of heat to be given to the generator is effected depending on changes in the temperature of the heating medium circulating through the evaporator or the temperature difference of the heating medium between the inlet and outlet thereof in accordance with a refrigerating or cooling load.
The control process described hereinabove cannot be adapted for the case where an absorption refrigerating machine including an evaporator of direct expansion type in which an air is directly cooled by the cooling (refrigerating) capabilities developed in the evaporator is used for air conditioning. The reasons for this are as stated hereinbelow.
In air conditioning, there are two types of cooling load, one being a sensible heat load and the other being a latent heat load. The sensible heat load is heat which is spent for lowering the temperature of the air to be conditioned, and the latent heat load is heat which is spent for lowering humidity of the air to be conditioned by condensing the moisture content of the air.
It is quite easy to obtain a sensible heat load based on the values of the inlet temperature of the air flowing into the evaporator and the outlet temperature of the air flowing out of the evaporator as sensed by a temperature sensor. However, difficulties are encountered in obtaining values of a latent heat load, which make it impossible to accurately grasp the cooling load. In the event that control of the cooling capabilities of a refrigerating system provided with a direct expansion type evaporator is carried out by the abovementioned control process, a lack of capabilities would result. The provision of means for sensing a latent heat load would enable acculate sensing of the cooling load to be effected. However, such sensing means poses the problems that the construction is complex and high in cost, and that the degree of accuracy with which sensing can be effected is low.